1. Field of Invention
The stabilization of annatto (bixin and norbixin), tomato (lycopene), carrot (beta-carotene), marigold (xanthophyll), and synthetic carotenoid pigments upon exposure to air with certain digestible surface-active agents, and synergistic combinations of such stabilized pigments with natural antioxidants which further increase their stability.
2. Background of the Invention and Prior Art
The foregoing natural and synthetic carotenoids are important food colors, various forms of annatto and other natural carotenoid colors having been used for at least a century, and synthetic carotenoids having been available since about 1950. The color and hue of tomato paste affects its value.
Carotenoids have more recently been shown to have anticarcinogenic properties, perhaps due to their ability to quench singlet oxygen. Beta-carotene in particular has been associated with inhibition of lung cancer on the part of smokers in epidemiological studies, due to its widespread prevalence in good diets. Other carotenoids, particularly lycopene found in tomato, and bixin and norbixin from annatto, have been shown to have equal or superior singlet oxygen quenching properties, and are also potential anticarcinogenic agents.
Perhaps because of their effectiveness in quenching singlet oxygen, or perhaps because of other properties, carotenoids in general degrade rapidly upon exposure to air, or under thermal stress, particularly when oxidative stress is also present. This makes them less satisfactory than so-called "coal-tar" colors for use in many foods, such as snacks, breadings, cooking oils, and dried cheeses, as well as in emulsified foods containing air as a result of the emulsification process, or in baked goods. If used as a food supplement, for humans or animals, the stability in the feed is also questionable, even though synthetic antioxidants may be available for feed use.
Even where the carotenoid is not exposed to air, as in liquid preparations, antioxidants are commonly added to eliminate the slight oxidative stress which may occur due to oxygen in the headspace of the container.
Encapsulation is one way of avoiding degradation of pigments, and this has been achieved by dissolving the pigment in a solvent, such as chloroform, admixing the solution at a high temperature with an encapsulating agent such as gelatin, and removing the solvent quickly. In certain cases, bisulfite is used to prevent degradation, but this is ojectionable as a stabilizer. Other systems use thiopropionates as antioxidants, but these are not permitted in foods. Yet other systems depend on combinations of polyoxyethylene derivatives combined with BHA and BHT in the presence of substances which are cosolvents for the pigment and polyoxyethylene derivatives to make stable liquid combinations, from which the pigment will not crystallize. As shown in this specification, the presence of the polyoxyethylene derivative is highly destabilizing in the presence of oxygen, and the BHA/BHT antioxidants are ineffective.
The prior art shows condimental combinations of seasonings, including oleoresins of carotenoids, with various emulsifiers to achieve mutual compatibility as well as dispersibility in both oil and water. These systems did not have as their objective the stabilization of the pigments against oxidative or thermal stress and, indeed, suggested deleterious combinations of emulsifiers in terms of the objectives of this specification.
Accordingly, the present art is in great need of non-toxic, natural, effective systems which will preserve the color of carotenoids and their oleoresins when used in the manufacture of food which is subject to oxidative stress. This invention provides the first such system, which is much more effective than even an ethoxyquin system.
The heart of the invention lies in the totally unexpected effect which certain, but not all, emulsifiers have upon the stability of these pigments. As described hereinafter, these emulsifiers are not antioxidants, and indeed may have a slight pro-oxidant effect when added to vegetable oils. Accordingly, the stabilizing effect must be attributed to an unknown mechanism, such as inhibition of electron transfer in the pigment when it quenches singlet oxygen, which then renders it more immune to the attack of oxygen. This, however, is only a hypothesis and not intended to be limiting.
Since the emulsifiers used in the stabilizing systems of this invention are readily digested by the enzymes secreted in the digestive tract, they will not block the electron transfer potential of the pigments after absorption by the body. Therefore, they will not impair their health benefits when a component of the diet. In this respect, no harmful additive, such as ethoxyquin, is introduced into the diet to preserve their effectiveness.
Various combinations of natural antioxidants with the carotenoid-emulsifier systems achieve stabilities which none of the substances can achieve alone, and indeed the stabilities achievable, for all practical purposes, are greater than a year, as opposed to a month using present art. This opens entirely new uses for carotenoid pigments.
Among the specific carotenoids which benefit from the present invention are bixin and norbixin, pigments derived from annatto, lycopene, natural beta-carotene, xanthophyll, and the synthetics beta carotene, beta-apo-8-carotenal, canthaxanthin, and astaxanthin. Natural forms of the latter equally benefit.
There are four fundamental aspects of this invention:
1. Certain emulsifiers greatly inhibit degradation, especially color degradation. PA1 2. Rosemary and other Labiatae extracts inhibit degradation to an extent much greater than their antioxidant power might suggest. PA1 3. Single and multiple synergism is expressed using the combinations which are possible as a result of this disclosure. PA1 4. Tocopherols and tea extract are also synergistic with combinations of the above.
As a consequence, particular stabilization systems can be developed for the specific carotenoid, carotenoid mixture, or food system involved which will preserve both the color and biological effect of the carotenoid.